TW200419041A - Anti-rewet press fabric - Google Patents

Abstract

An anti-wet press fabric for paper and board machine includes a barrier layer such that during compression in the press nip, the water is forced through the barrier layer, but is prevented from flowing back to the paper web during expansion. The barrier layer comprises a continuous material possessing, for example square, rectangular, tetrahedral, circular or oblong conical inclusions with a smaller opening on the bottom than on the top of the structure. Each of these "funnels" effectively constitutes a one-way valve and creates a vacuum to prevent re-absorption of water by the paper sheet. Under pressure, the structure of the barrier layer allows water to flow into the cones and out of the smaller opening in the bottom. Upon expansion, the smaller opening in the bottom of the structure restricts backward water flow and creates a vacuum on the other side. The vacuum increases water retention in the press fabric and prevents rewetting of the paper sheet. Another embodiment of the invention is described herein, wherein the barrier layer exists as a separate fabric fed through a press section. In this embodiment, the "separate fabric" can just be "conical inclusion sheet" itself. That is, the sheet itself constitutes an inventive belt having anti-rewet properties.

Description

200419041 Description of the invention: I: Technical field of the inventor 3 Field of the invention The present invention relates to a supply with several tapered openings for anti-wetting in the press section of a paper making machine 5 Flattened fabric. I: Prior Art 3 Background of the Invention During the papermaking process, a fibrous fibrous web is moved by depositing a fiber slurry (that is, an aqueous dispersion of cellulose fibers) onto a forming area of a papermaking machine. It is made on a forming fabric. A large amount of water flows from the slurry through the forming fabric, leaving a fibrous fibrous web on the forming fabric. The newly formed fibrous fibrous web advances from the forming zone to a flat nip, which contains a series of press nips. The fibrous fibrous web 15 passes through several press nips supported by a flattened fabric, or, as is usually the case, between two such flattened fabrics. In the press nip, the fibrous I4 raw fiber web is attracted to the compression force (CommpesSiVe focrce), which will squeeze out water, and will adhere the cellulose fibers in the web to another web. Turn the fibrous web into a cardboard. Water is absorbed by the flat fabric or fabrics and ideally will not return to the cardboard. The paperboard finally advances to a dryer zone which contains at least a series of rotatable drying cylinders or cylinders which are heated internally by steam. The newly formed cardboard is then introduced into a spiral path around each of the series of cylinders by a dryer fabric. The 5 = woven fabric will press the cardboard tightly against the surface of the cylinders. . The heated θ hunt reduces the water content of the cardboard to a desired level by volatilization. It should be explained that all the fabrics of the flattening and drying machines are in the form of endless loops on the paper machine, and act on the side of the conveyor. What needs to be further understood is that paper manufacturing is a continuous process that progresses at an impressive rate. That is, fibrous sludge is continuously deposited on the forming fabric in the forming area, and the newly manufactured cardboard is continuously rolled into a drum after it comes out of the drying area. The present invention relates in particular to flattened fabrics used in flattened nips. Laminated fabrics play a key role during paper manufacturing. As implied above, one of its functions is to support and transport paper products made through the press nip. Laminated fabrics also participate in the finish of the cardboard surface. That is, the flattened fabric is designed to have a smooth surface and a uniform elastic structure so that on the way through the press nip, a smooth, unmarked surface is created on the paper. Traditionally, flat nips have consisted of a series of nips formed by pairs of adjacent cylindrical rollers. In recent years, the use of long press nips of the shoe type has been found to be better than the press nips formed by pairs of adjacent press rolls. This is because it takes longer for the web to pass through a long press nip than through a press roll formed by a press roll. The longer a net can be introduced into the nip and exposed to dust, the more water can be removed there, and therefore, the less water that remains in the net and needs to be removed by vaporization in the dryer zone. In these various long flattening presses, the nip is formed between a cylindrical pressing roller and a fox-shaped pressure shoe plate. The latter has a cylindrical shape with a curvature close to the radial center of the cylindrical dust roller (flat pressure), which is correspondingly longer. The effect of this newly formed long-pressing technology has magically increased the dewatering of the fibrous web in the long-pressing rollers when compared to traditional ones on paper machines. When the shoe plate is configured to be in close physical proximity to the other ... a pressing force is opened in the machine direction by 5 to Satoshi, which is longer than the pressing roller formed between the two pressing rollers. Since the long pressing roller system is 5 to longer than the traditional one, the traditional pressure is equal to the pressure, the so-called residence time of the fiber web in the long pressure is the same as the pressure per square inch of the leaf (is used Yu—The flat pressing of the hoof plate in the shape of a two-dimensional flat requires a special strip, as shown in US Patent No. 5,238,537. This strip is designed to protect The support, conveying and dewatering of the flat fabric, within the fixed pressure display range, are protected from accelerated wear that may result from direct, sliding contact. This-strip system must have-smooth, impervious Surface, the surface will dde or slide over the fixed shoe plate on the oil film. The strip is moved through the roller at approximately the same speed as the flat fabric, thereby making Laminated fabrics suffer the least amount of friction against the surface of the straps. Perhaps most importantly, laminated fabrics accept a large amount of water extracted from the press nip in the press nip. To achieve this function, there must be a space, Generally referred to as pore volume (void v〇iume), Water is supplied into the flattened fabric, and the fabric must be sufficiently penetrable to water during its entire useful life. Finally, the flattened fabric must be able to prevent the water that is wetted by the paper from leaving the pressured area Time to return and moisten the paper. Contemporary flatbed fabrics are created in a wide variety of forms. 'For the paper grades you want to make, flatbed fabrics are designed to fit the paper machine they are installed on. In general, it includes a woven 5 base fabric that has been needle-rolled into a fine, non-woven fibrous material. The base fabric can be made of single fiber, plied single fiber, multifiber, or plied Re-signed yarns are woven and can be single-layer, multi-layer or laminated. These yarns are typically extruded from many synthetic polymer resins, such as polyamide and polyester resin, Paper machine covers are technically used by generally 10 artisans for this purpose. The woven base fabric itself has many different forms. For example, woven endless, or Weaving and then making it into a circular form with a woven seam. Alternatively, it can be made by a method generally known as endless weaving, in which the width of the base fabric 15 in the The side is equipped with a seam loop using its machine direction (MD) yarn. In this method, the machine direction yarn is continuously woven back and forth between the width direction edges of the fabric, on each side Turn back and form a sewing loop. The base fabric manufactured in this way is placed in a loop when it is mounted on a paper machine, and for this reason is referred to as a 20-seamable on-machine seam (〇n -machine-Seamable) fabric. In order to make such a fabric into a loop, the two widthwise edges are put together, the sewing loops on the two edges are interlaced, and a needle or pivot is guided Channels formed by these staggered sewing rings. Furthermore, the woven base fabric can be laminated by placing a base fabric in a loop formed by another base fabric 8 and forming a base fabric. Needle rolling through the two base fabrics, to join them together One or both of the woven base fabrics may be in a form that can be sewn on the machine. 3. In the flattening area of the paper machine, the formed paperboard is flattened to a higher dry content through the continuous pressing area. The paperboard is conveyed through the press nip together with one or more bad-shaped woven fabrics, which are generally referred to as flat press fabrics. When talking about flatbed fabrics, many theories have been proposed to explain what happens to paper webs and flatbed fabrics during flattening. The mechanical press system applied to the paper web and flat fabric is the same, and the hydrodynamic pressure in the web is considerably higher than the fluid dynamic pressure in the fabric. This pressure differential provides the driving force for the transfer of water from the web to the fabric. Paper nets or paperboards, and flat-pressed fabrics reach a small thickness at about the same time (slightly close to the middle pressure It). Cardboard is considered to reach the maximum dryness of the basin at the very same moment. After that, the cardboard and fabric started to decompress. During this decompression period, a space is created on the surface layer of the paper web and the flattened fabric, both of which have been compressed to a minimum thickness under a maximum pressure. Along this space, water flows back from the inside and possibly from the bottom of the fabric to the surface of the fabric, and enters the cardboard to restore the pressure balance. This decompression phase provides re-wetting of the cardboard in the press nip. In the construction of the flat fabric of the prior art, a fabric with a surface layer facing the paper net is generally formed in practice. The surface layer is much denser than the back of the structure 'and is used, for example, on the opposite side of the net. It is not uncommon for the fibers to be oriented toward 200419041 to reduce flow resistance. During the decompression phase, the high capillary forces, together with the large spaces in the flat fabric structure, absorb moisture from the open back structure to the surface layer, quickly reducing the space in the surface layer. When the space of the paperboard rises to a high level during leaving the press nip and the flow resistance of the flattened fabric against the paperboard is reduced, the combined rewetting and low paper dry content are caused. There are prior art concepts that teach fabrics with conical- or funnel-shaped openings (see, for example, WO 86/05219 and EP 0103376), none of which has small ends that are not counted to open and close In order to let the water flow in a direction that only passes through the 10 ends, it acts as a separation layer in the flattened fabric under pressure to prevent rewetting. In general, woven base fabrics are typically in the form of endless loops' or sewable to have a specific length (measured near the lengthwise direction) and a specific width (measured near thereacross) ) The opening ^ 15. Because paper machine configurations vary widely, paper machine cover manufacturers are required to produce flat fabrics, as well as other paper machine covers, to the extent that they are required to fit specific parts of their customers' paper machines. Needless to say, this requirement makes it difficult to make the manufacturing process smooth, as each flatbed fabric typically must be ordered. 20 In response to the demand for faster and more efficient production of flat fabrics of various lengths and widths, flat fabrics have generally been produced in recent years using a spiral technology, which was disclosed in The teachings of U.S. Patent No. 5,360,656 to Rexflex et al. Are incorporated herein by reference. 10 200419041 Wu Guo Patent No. 5,36,0,656 shows a flat woven fabric comprising a base fabric having—or more layers of needle-punched staple fiber material therein. The substrate, the object includes at least one layer composed of a spirally bent strip system of a woven fabric. The woven fabric has a width smaller than the width of the base fabric. The bottom fabric is loop-shaped in the longitudinal or machine direction. Spiral curved strip :: The long thread forms an angle with the length direction of the flat fabric. The strips of the weaving two, which can be plain-woven on a loom, are narrower than those typically used for paper machine cover manufacturers. The base fabric consists of a number of fairly narrow loops with twists and turns. (At the age of 11 ▼. Far-woven fabric strips are woven with long (warp) and cross yarns). The adjacent turns of the spirally curved fabric strips may be adjacent to another 2 ' and the resulting spiral continuous stitching may be stitched, rotated: cored, welded (e.g. ultrasonic) or glued. Alternatively, the adjacent long sides of the connecting snail may be arranged overlapping, as long as the sides have the thickness of Chengxi so as not to increase the thickness of the overlapping area. The spacing between the longer yarns can be increased at the edges of the strip. In this way, when the spiral turns are arranged overlappingly, there will be a constant spacing between the long φ and giant in the overlapping area. . (Explanation of the invention) Summary of the invention. January is an anti-rewetting flattened weave for paper and cardboard machines. One of the objects of the present invention is to suppress the level of the paper web by obstruction during the aforementioned decompression phase. Press the fabric side to make and maintain a space to make it moist. In order to achieve this, the anti-rewetting flattened fabric 11 200419041 has a cone made of several cones with several small ends. Layer, when the water level is in the compression zone of the press nip, is pressurized and passes through the ends, and the ends are closed to prevent backflow and provide water absorption in the cone when the pressure is released. 5 more In particular, the flat-laminated fabric of the present invention comprises a continuous material having, for example, annular, quadrangular, and / or conical inclusions with a smaller opening at the bottom of the structure than at the top. These "funnels" Each of them constructs a one-way valve and creates a space to prevent water from being reabsorbed by the cardboard. Under pressure, in the compression area of the press nip, the% 10 structure allows water to flow into the conical structure Co-current Smaller opening at the bottom. When the pressure in the decompression zone of the pressure roller is released, the small opening at the bottom of the structure restricts the water flow in the opposite direction and creates a space on the other side. The space will increase The moisture in the flattened fabric retains and inhibits water re-absorption into the paper. 15 This structure can be contained inside a needle-rolled flattened fabric as a substrate for separating the fabric through a round-pass nip, or as a A delicate surface with a needle-punched batting, a finely woven bottom layer, or a non-woven flat structure. The bottom layer of a plain fabric. 20 The water-repellent fabric, in its simplest form, can include- First layer. Surface layer 'and-Second layer 4 and a barrier layer, the barrier layer is located at ρ of the surface layer. The surface layer is located in the flattened fabric facing and conveying the net to be dehydrated. Compared to the surface layer, The barrier layer has a high flow resistance claw dynamic resistance in its thickness direction, so that the moisture and air that are pressed through the barrier layer during the compression of the paper web and the flattened fabric (derived from the pressure of the flattening 12 200419041 load) in the space to When the press fabric and the paper web are formed during the decompression period when they leave the press nip, they are prevented from flowing back in the barrier layer in a large amount. That is, during the compression of the flat fabric in the flat nip during operation, 5 is quite south. Pressure forces water and air from the surface structure of the cardboard and flat fabric to flow through the second layer. In this regard, when a so-called vented press is used, the second layer may constitute The bottom layer of the flat-pressed fabric of vented bdt in a low-pressure press zone or a shoe press. 10 Minus the invention-a specific example, the barrier layer is made of-a polymer with a large number of conical inclusions A layer of sheets. These "funnels" in this layer are so configured and have a narrow opening at the bottom that allows water to pass at the highest pressure during the compression phase, but effectively blocks the Reverse water flow caused during the decompression phase. 15 Another specific example of the present invention is described herein, in which the barrier layer is present as a separate fabric that is transported through and flattened. In this specific example, the "split fabric" may be exactly the "conical inclusion body layer" itself. That is, ^ itself constructs an inventive conveyor belt with anti-rewetting properties. The invention will now be described more fully and in detail, often with reference to the drawings identified below. Brief Description of the Drawings Figure 1 is a perspective view of a flattened fabric; Figure 2 is a schematic cross-sectional view of one of the re-wetting resistant flattened fabrics of the present invention located in the flattening area of a paper machine; 13 200419041 Figure 3: The present invention- Flattened fabric-a cross-sectional view of another specific example; and Fig. 4 is a schematic cross-sectional view of one of the re-wetting resistant conveyor belts of the present invention located in the flattening section of a paper machine. 5 [Embodiment] Detailed description of the preferred embodiment

Referring now to FIG. 1, there is shown schematically a flattened fabric 10 having an inner surface 12 and an outer surface 14. As shown in FIG. The flattened fabric shown is a machine-sewnable form with a stitching area 16, which may include-a seaming mechanism suitable for use in a form well known in the paper making industry. Of course, the The flat fabric can also be woven endless or spiral. Referring to FIG. 2, the pressing nip 20 includes an upper pressing roller 22 and a lower pressing roller 22. Preferably, the lower pressing roller 23 is formed with a plurality of suction holes (suction form).

Cavities of 15 'These suction holes have vacuum, elongated grooves or blind-drilled holes. A paper web% and a flattened fabric 10 are conveyed through the press nip 20. As shown in FIG. 2, the flattened fabric 10 (in its most common form) includes a first or surface layer 26, which is connected to a second or barrier layer 27, and a can 20 which is a loop woven Base support 28 of an endless woven base. The surface layer 16 is composed of, for example, a synthetic needle-rolled fiber batt (structure integrity is appropriately enhanced), a worsted base material, or a non-woven structure. # 序 皮 Set to make direct contact with the paper web 24. The barrier layer 27 is located on the surface layer 26y, and is superimposed by, for example, a cone with many conical inclusions or channels 30. ^ & 14 200419041

Murethane) plate, these holes 3◦ have at the bottom-smaller than the top opening 32. These layers (including the entire flat fabric) can be regarded as having two stages by the action of pinching the nip 20. At the 5th stage, the paper web 24 and the flattened fabric are compressed by the force generated by the pressure of the pressure m. In this compression stage, the paper web M and the surface layer% are taken to have a small thickness and pore capacity, and the inclusion body composed of water and air flows from the bottom of the structure to the pressure roller 23.

The barrier layer 27 is also heavily compressed during the compression phase. The water and air portions are pressed out of the paper web 24 and the surface layer 26 by 10 minutes, and partially pass through the barrier layer 27 to the holes in the pressing roller 23. Water can pass through the barrier 27 due to the high pressure in the pressing pressure _ between the pressures 23 and 23. That is, under pressure, water will flow into the larger top opening 32 of the conical channel 30 in the barrier layer 27, and flow out of the relatively small opening 34 at the bottom. Note that these channels 3G can be arranged at a predetermined distance from each other in the machine direction (his) and transverse direction (CD) directions throughout the length and width of the fabric. "

When the web 24 and the flat woven reed have been compressed to a maximum value (near the midpoint of the nip 20), the web 24 is considered to have reached its maximum dry content. Then the second phase (decompression phase) begins. When depressurized, the smaller openings 34 in the bottom of the channels 30 restrict the flow of water in the opposite direction and create a space (vaeuum) on the other side of p and the partition $. This space increases the retention of water on the flattened fabric 10 and prevents water from being reabsorbed into the paperboard. Therefore, the paper web 24 is not re-wetted to any noticeable amount, and a paper board having a higher drying amount than that obtained by other methods is obtained. The surface layer 26 shields the opening of the barrier layer 27 from the paper web, and conveys the paper web 24 through the flattening area under any bad paper markings. / The specific examples of the invention that have been described are only considered as an example, and it is possible to make it possible. For example, the barrier layer 27 can be covered inside a needle-punched C fabric 'or exist as the bottom layer of a pressed-pinned fabric (the pressed fabric / with a needle-punched batt, a worsted substrate, or-non-woven) The structure is composed of 'Tianzhi surface'. In addition, it can be used as a substrate for fabrics that are separated by feeding through one of the nips. _ 10 Where the variation of the presence of the barrier layer as a separate fabric is described. In this specific example, the "r-separated fabric" may be exactly the "conical 03 body layer" itself. That is, the layer itself constructs a band 27 having anti-rewetting properties, as shown in FIG. 4. As shown in FIG. 4, a paper web 24, a flattened fabric 10, and a strip 27 are transported through the press nip 20 as shown in FIG. Continuing to refer to FIG. 4, it should be understood that the strip 27 is located under the flattened fabric 41. That is, as shown by φ 胄 in the figure, the strip 27 is not a part of the flattened fabric 41. Finally, for stability, the strip 27 further includes a support member (20 not shown in the figure). It should be apparent that the strip 27 inhibits rewetting in a manner similar to the barrier layer 27 shown in Fig. 3. These anti-wetting mechanisms have been discussed in detail previously, so the discussion of these mechanisms is omitted here. Furthermore, although the channel 30 shown in FIG. 2 is conical, it may be of the same type, such as a generally circular, oval, square, rectangular, and tetrahedral shape, as long as the top opening is larger than the bottom opening. For example, as shown in FIG. 3, the opening 30 ′ is square, rectangular, and tetrahedral at the top opening 32 ′, and tapers down to the bottom opening 34 ′, which may be the same or not. The same type, as long as it is small.

In this way, the purpose and advantages of the present invention have been understood, and although better specific examples have been disclosed and described in detail herein, its scope is not limited thereby; instead, its scope should be covered by the patent application attached below Scope to decide. 10

17 200419041 L Schematic illustration 3 Figure 1 is a perspective view of a flattened fabric; Figure 2 is a schematic cross-sectional view of one of the anti-rewetting flattened fabrics of the present invention located in the flattening area of a paper machine; A cross-sectional view of an alternative specific example of a flat fabric of the invention; and

Fig. 4 is a schematic cross-sectional view of one of the anti-rewetting bands of the present invention located in the flattening zone of a paper machine.

[Representative symbols for the main elements of the figure] 10, 41 Flat fabric 24 Paper net 12 Inner surface 26 Surface layer 14 Outer surface 27 Barrier layer, strip 16 Stitching area 28 Bottom carrier 20 Squeeze nip 30 Hole 22 Roller 32, 32 'top opening 23 Lower pressure roller 34, 34' bottom opening 18

Claims (1)

200419041 Scope of patent application: 1. An anti-rewetting flattening fabric for dewatering a fiber web in a flattening area of a paper machine. The fabric having an inner surface and an outer surface includes: 5 a first Layer, the first layer is a surface layer on the outer surface for supporting the fiber web; A second layer, the second layer is a barrier layer below the surface layer and has a high flow resistance in a thickness direction from the inner surface to the outer surface; 10 the second layer is a plurality of inclusions Polymer layers, the inclusions are channels for water from the fiber web to flow through, and the second layer is connected to the surface layer; and each inclusion is tapered to have an abutting surface layer 15 openings at the top and a bottom opening at a distance from the surface layer, and the bottom opening is smaller than the top opening to prevent the liquid in the The flattened fabric flows back to the surface layer as it leaves a press nip. 2. The anti-rewetting flattened fabric according to item 1 of the patent application scope, wherein the surface layer is composed of needle-punched batting. 3. The anti-rewetting flattened fabric according to item 1 of the patent application, wherein the surface layer is composed of a worsted base material. 4. The anti-rewetting flattened fabric according to item 1 of the patent application scope, wherein the surface layer is composed of a non-woven structure. 5. As for the re-wetting-resistant flattened fabric of the scope of application for patent No. 1, wherein the shape of the inclusion body is a circular tapering shape from the top opening to the bottom opening 19 200419041. 6. The anti-rewetting flattened fabric as claimed in item 5 of the patent application, wherein the shape of each opening is square, rectangular, quadrangular, circular or oval. 7. For the anti-rewetting flattened fabric of item 1 of the scope of patent application, the shape of each 5 openings is square, rectangular, quadrangular, circular or oval. 8. The anti-rewetting flattened fabric according to item 1 of the patent application scope, further comprising a base fabric under the second layer, and wherein the surface layer is a needle rolled to the second layer and the Non-woven batt consisting of short fibers of a base fabric. 10 9. The anti-rewetting flattened fabric according to item 1 of the patent application scope, comprising a bottom carrier having a surface layer, the surface layer being selected from a needle-punched batting, a worsted base material and a non-woven fabric. A group of structures. 10. The anti-rewetting flattened fabric according to item 9 of the application, wherein the second layer is located between the base carrier and the surface layer. 15 11. An anti-recycling device for dewatering a fiber web in a flat nip of a paper machine Wet flattened fabric, the fabric having an inner surface and an outer surface includes: a first layer, the first layer is used to support a second layer; the second layer is a barrier layer, which is The inner surface has a high flow resistance in the thickness direction of the outer surface 20 surface; the second layer is a polymer layer with a plurality of inclusions, which are channels for water from the fiber web to flow through And the second layer is connected to the surface layer; and 20 200419041 each inclusion body is tapered to have a top opening at the outer surface and a bottom opening spaced from the outer surface, and the bottom opening It is smaller than the top opening to prevent liquid from flowing back from the bottom opening to the top opening. 5 12. The anti-rewetting flattened fabric according to item 11 of the scope of patent application, wherein the shape of the inclusion body is a conical shape that tapers from the top opening to the bottom opening. 13. The anti-rewetting flattened fabric according to item 11 of the application, wherein the shape of each opening is square, rectangular, quadrangular, circular, or oval. 10 14. The anti-rewetting flattened fabric according to item 11 of the application, wherein the first layer is woven, non-woven, spiral-formed, or a laminate. 15 · An anti-rewetting belt for dewatering a fiber web conveyed by a flattened fabric in a flattening area of a paper machine, the belt having an inner surface and an outer surface; 15 The tape is a barrier element located under the flat fabric and A high flow resistance in the thickness direction from the inner surface to the outer surface; the belt is a polymer layer having a plurality of inclusions which are channels for water from the fiber web to flow through; and each The inclusion body is tapered to have a top opening of 20 at the outer surface and a bottom opening spaced from the outer surface, and the bottom opening is smaller than the top opening to prevent liquid from leaving the flat fabric A press nip flows back to the flattened fabric. 16. The anti-rewetting belt according to item 15 of the application, wherein the shape of the inclusion body is a cone 21 200419041 that gradually tapers from the top opening to the bottom opening. 17. For example, the anti-rewetting band of item 15 of the patent application, wherein the shape of each opening is square, rectangular, quadrangular, circular or oval. 18. If the anti-rewetting zone of the scope of application for item 15 of the patent, it further includes a five-story building. twenty two